Corrosion Cause Analysis of a Surface Pipeline Flange

Abstract

Corrosion was found on the inner wall and sealing groove end face of a surface pipeline flange in an oilfield in western China after one year’s service. Corrosion causes were investigated by physical and chemical property tests, metallographic examination, scanning electron microscope, scanning electron microscopy(SEM) inspection, energy disperse spectroscopy(EDS) analysis and X-ray diffraction(XRD) analysis. The results showed that the chemical composition and mechanical properties of the flange were all in accordance with the corresponding parameter requirements, and the corrosion phenomenon was mainly attributed to CO2 corrosion. High temperature and high medium flow rate also had a big influence on the acceleration of the corrosion process. Corrosion of the sealing groove end face was attributed to galvanic corrosion, the corrosion potential difference between the flange and gasket was the main reason for the galvanic corrosion.